As the number of applications used for basic, everyday functions offered on mobile devices continues to increase, reliability of such applications becomes more important. Many of these applications may be categorized as high power or high sensitivity radio frequency (RF) applications, wherein using such an application is associated with relatively large power consumption. Notably, such high power or high sensitivity RF applications commonly generate distortion of RF signals, particularly in the form of harmonic distortion. This distortion of RF signals causes RF signal degradation, thus reducing the RF performance of the mobile device.
In particular, harmonic distortion may be generated by both the RF components and by the packaging (i.e., the substrate) in which such RF components are housed. Thus, one way to reduce the harmonic distortion is by employing RF microelectromechanical systems (MEMS) devices as the RF components in the mobile device. RF MEMS devices, such as tunable capacitors and metal contact switches, are passive devices with moving mechanical elements that deliver the desired electrical function. Notably, RF MEMS devices typically generate very low levels of signal distortion, and thus, may reduce the overall harmonic distortion of a high power or high sensitivity RF application.
However, even when employing RF MEMS devices, the substrate on which such RF MEMS devices are manufactured or under which they are capped generates harmonic distortion that can significantly contribute to overall RF distortion. While methods exist to mitigate or reduce the harmonic distortion generated by the substrate, such methods have tradeoffs. For example, one method to reduce the harmonic distortion associated with the substrate is to include metal shielding that separates RF signals from the substrate. While such metal shielding may reduce the RF distortion to a desired level, the metal shielding may introduce loss or static ground capacitance, which reduces overall RF performance. Additionally, methods such as metal shielding are typically expensive to implement.
Accordingly, there is a need for a less expensive alternative for packaging RF MEMS devices that is capable of operating at high power with reduced harmonic distortion attributable to the package.